Deaver performed the work in the five cases an independent auditor deemed most troubling.

Deaver's work - and the practices of the SBI - came under fire in February when Greg Taylor, a Wake County man, was exonerated after 17 years in prison. Deaver withheld results of more sophisticated blood tests that yielded negative results. He reported to prosecutors that Taylor's SUV gave chemical indications for the presence of blood.

Deaver testified in February that supervisors told him to report his findings that way. According to the audit released Wednesday, the practice was widespread. Eight analysts completed their reports in a similar fashion.

"This is a damning indictment of the entire serology section," said Mary Pollard, executive director of Prisoner Legal Services. Her agency will begin reviewing the cases of 80 defendants who are currently in prison. "It is absolutely horrifying."

The criminal convictions or sentences of three people who have since been executed in North Carolina, and four more cases in which the defendants are now on death row, are may be in doubt because of flawed reports.

Chris Swecker, a former FBI agent who audited serology work from 1987 to 2003 said in the report that the questionable work is the result of "poorly crafted policy; lack of objectivity; the absence of clear report writing guidance; inattention to reporting methods that left too much discretion to the individual Analyst; lack of transparency; and ineffective management and oversight..."

According to the review, the cases involved SBI lab reports that were overstated, misleading or omitted important information about negative test results that would have been favorable to the defendants.

The SBI's lab work is often powerful evidence in criminal cases, shaping decisions at the heart of a defense that include decisions about plea bargaining or how to cross examine witnesses.

The SBI has followed more updated procedures on blood analysis since 2003, and more recent work is not under scrutiny. "The tests that are examined in the bulk of this report are no longer in use," the agents wrote.

The serology unit has been under intense scrutiny since February when, in the case of Taylor, it was shown that SBI agent Duane Deaver reported to prosecutors that the fender of Taylor's SUV gave chemical indications for the presence of blood.

But according to lab notes discovered in 2009, Deaver had performed more specific tests, which registered negative results for the presence of blood. He never mentioned those results or the additional tests; at Taylor's hearing in February, Deaver testified that his superiors taught him to write his reports like that.

The new report says that Deaver gave "inaccurate" testimony before the Innocence Commission in the hearings that resulted in Taylor's exoneration when he testified that he was following policies. There were no such policies then, the report says, though it was the SBI's practice at the time to omit negative results in some cases. It became the agency's actual policy in 1997.

One of the defendants who has been executed is Desmond Keith Carter, who had confessed to a March 1992 murder. The report says Deaver in that case "confirmed the presence of blood despite a negative confirmatory test." The questionable evidence wasn't introduced at the trial, according to the report.

Preliminary, or presumptive, blood tests can give false reads; those tests often give positive results for substances such as metals, plants and animal matter. More sensitive tests are seen as confirmatory.

Swecker and Wolf examined more than 15,000 old cases involving serology work to identify the cases similar to the Taylor case.

The former agents said they could not conclude that each case has a wrongful conviction, but said each will need to be reviewed by defendants, prosecutors and, in some cases, the courts.

"This will require an in depth review of investigative case ... files that are located in the records of law enforcement departments across the state, court records, trial transcripts, laboratory files, appellate records, records of the Administrative Office of the Courts and any other relevant material," they wrote.